1. Field of the Invention
The invention relates to a breakout warning method in a continuous casting installation in which measurements are taken in the area of an ingot mold and changes in the measuring results are monitored by an apparatus operating according to such method.
2. Description of the Prior Art
In a manner known from prior art continuous casting installations, liquid steel is cast from a distributing unit into a water-cooled ingot mold, usually a copper mold. This mold is reciprocated at a frequency of approximately 1.5 Hz in the direction of travel of the continuous casting. Normally, between the poured steel billet and the ingot mold a lubricating film is maintained which is obtained from a lubricating substance specially provided therefor. As is known, an outer jacket of the charged liquid steel solidifies in the mold so that it acquires a certain strength. The poured steel billet or ingot can thereby support itself at the bottom of the mold and can be pulled out continuously from the mold.
During the practical operation of such a continuous casting installation, unpredictable breakdowns occur from time to time during which the outer jacket of the billet ruptures in an undesirable fashion resulting in a "breakout." This is attributable to the formation of bakings between the cast-on steel and the mold which cause the steel jacket that has already solidified and supports the billet to burst within the mold. If this burst spot does not acquire adequate strength again by cooling before the liquid steel leaves the mold, the steel will "breakout" and flow into the installation, disturbing the production run.
The baking referred to above is a solidified mass of steel permanently bonded to at least one wall of the mold. In the mold the outer shell of the strand continuously solidifies and leaves the mold when the shell thickness is sufficient, i.e., when the strand is self-supporting. If the shell of the strand is not thick enough, it may rupture or re-liquify. Molten steel then pours out without forming a strand. Normally a baking does not entirely block the mold to stop the flow of metal, but only a local baking occurs. This is worse than a total blocking. Local bakings change the flow characteristics of molten steel in the mold and thus prevent the formation of a sufficiently stable shell.
A prior breakout warning method is well known as a result of experiments during which the hoisting speed of the mold is measured and changes in the speed are monitored. This method does not always work satisfactorily.